The invention concerns a roll press of the type having two press rolls forming with each other a press gap, and having axes situated in a press plane. A journal is disposed on the ends of each roll, with pillow blocks for receiving the journals and a rack for supporting the pillow blocks. Tie rods are arranged on both sides of the press plane, and are generally parallel to it.
Roll presses are known in a plurality of embodiments. Only exemplary reference is made to DE 41 10 205 A1. Here, two press rolls are arranged in a way such that the press plane extends vertically and the press frame, consequently, is of an upright arrangement. There are varying arrangements known as well.
U.S. Pat. No. 4,837,907 describes a roll press with two rolls where the pillow blocks of the one roll are by means of screws fastened to the pillow blocks of the other roll. In the load state, the screws must transfer high tension forces, corresponding to the compression force prevailing in the press gap.
On the categorial roll press, the pillow blocks of the one press roll and those of the other press roll are joined by tie rods which are bendable with relative ease; moreover, the pillow blocks of the one press roll are axially movable in relation to the pillow blocks of the other press roll. This embodiment has several advantages: to begin with, the tie rods are capable of transferring the necessary tension forces. Furthermore, this embodiment allows a quick release and restoration of the coupling between the pillow blocks of the one roll and those of the other. Lastly, this embodiment allows in the case of different length changes of the two rolls a relative movement between both, including their pillow blocks, without creating stresses. This embodiment of a press has proved to be very suitable, for which reason the invention is based on it.
But it has been demonstrated that the said tie rods cannot always be fashioned as bendable as is necessary to avoid stresses. A forced bending of the tie rods can occur, specifically when the axial displacement between the two rolls becomes very large as the result of an extremely different axial expansion. Thus, the tie rods are stressed not only by design tension, but additionally also by an undesirable degree of bending.
The problem underlying the invention is to fashion a roll press in such a way that the tie rods will be stressed extensively by tension.